1. Field of the Invention
The present invention relates generally to painting equipment and more particularly to painting equipment controllers for automotive painting applications.
2. Description
While the theory of automotive paint chemistry and its application to various substrates has advanced considerably in the past decade, the bulk of that knowledge has rigidly stayed within the laboratory. Only a small portion of that laboratory knowledge has permeated the automotive plant environment. This has mainly resulted from the abstruse nature of the laboratory-derived knowledge and the requirement that the scientist or technical expert must be integrally involved in applying the theoretical knowledge.
Scientists in the laboratories have performed complex design of experiments to study the interrelationships between painting factors and painting responses. Their work has produced mathematical models which are typically very intricate so as to require three-dimensional depictions of the interrelationships (as shown for example in FIG. 1).
The various surfaces in FIG. 1 show an exemplary interrelationship between three painting factors and one painting response. The painting factors may be the settings of the painting spray gun, such as bell speed, shaping air, and bell fluids. The painting response may be an attribute of the sprayed paint, such as paint's gloss value. FIG. 1 illustrates how changes in the painting factors affect the painting response. For example, surface 20 shows what parameters of the painting factors produce a response value of "30". As shown in FIGS. 2a-2b, contour plots can be used to depict interrelationships between painting factors and a painting response in a two-dimensional view.
To use the experimental results in the automotive plant, the contour plots were studied to determine the optimal painting factor which would achieve a particular painting response. To determine what were the painting factors needed to achieve a desired level for two painting responses, the contour plots for two painting responses were placed on top of each other (see FIG. 2c); thereupon painting factors were determined based upon the area common to both desired painting response levels. The difficulty for analyzing the contour plots dramatically increases with the number of painting factors and responses involved.
The design of experiments approach was not used within the ever-changing plant environment when the painting factors and responses had to be changed from the initial laboratory-determined set of optimal painting factors. The unwieldy manner of the contour plots to effectively address the ever-changing painting factors and responses within the plant environment hindered their ability to assist in modifying the painting factors. Accordingly, modifications to the painting factors within the plant to achieve desired painting responses was an art form. This art form was to be learned from years of experience in controlling the painting equipment within the automotive plant. Due to these reasons, the automotive plant environment lacks the design of experiments approach for controlling paint equipment, especially for realtime or near-realtime control in reacting to changes in the plant environment or to changes in the painting equipment itself.